Genetic Theory of Harry Potter, The

By Stephen Mihm

Published: December 11, 2005

This summer, the journal Nature published ''Harry Potter and the Recessive Allele,'' a letter that argued that J. K. Rowling's tales of the young wizard Harry Potter offer an opportunity to educate children in modern theories of heredity.

As almost everyone above the age of 3 knows, the Harry Potter novels depict a world divided into people who possess magical powers (wizards and witches) and those who do not (Muggles). Not everyone can be a wizard; indeed, after careful review of the evidence, the authors of the Nature letter concluded that wizards evidently inherit their gifts from their parents as predicted by the theories of the 19th-century geneticist Gregor Mendel.

Apparently, wizardry (or the lack thereof) is determined by a linked pair of genes, or alleles, that you inherit from your parents, one allele from each parent. The researchers hypothesized that wizardry is a recessive trait, like blue eyes, meaning that an individual who inherits from his parents one wizard allele and one Muggle allele (wM or Mw) will not display wizarding powers. Only individuals with two wizard alleles (ww) will display magical powers. Such individuals -- like Harry and his nemesis, Draco Malfoy -- are more likely to be born to parents who possess ww genes.

But children born of mixed marriages need not necessarily live a life of Mugglehood: those with a pure-blood wizard father (ww) and a part-Muggle mother (Mw) can inherit the precious ww genes. Children can also inherit the trait when neither parent is a wizard but both carry the wizard gene (Mw). Here the researchers cited Harry's friend Hermione Granger, the child of two Muggle dentists, as an example of the recessive allele surfacing against the odds.

Case closed? Not a chance: no sooner had the letter appeared than a group of plant scientists at Cambridge fired off a rebuttal: ''Harry Potter and the Prisoner of Presumption,'' in which they claimed that the recessive-allele hypothesis was ''deterministic and unsupported by available evidence.''

Given Rowling's penchant for plot twists, details may yet surface that prove once and for all that wizarding is indeed a recessive trait. Until then, Rowling, whom religious fundamentalists have pilloried for glamorizing witchcraft, may well be preaching a far more subversive message, one that leads young readers to pursue the study of heredity, genes and -- inevitably -- evolution. Stephen Mihm

Drawing: The Genetic Theory of Harry Potter (Drawing by Knickerbocker)